Trying to boot a PE 4 in a VM not configured as Windows 8 makes no sense at all.
Why do you try that ?
Similar example would be : fix a 2003 VM with booting into Knoppix.
For that one boot you would configure the VM to use Linux as guestOS - otherwise the mouse would work horrible.
In this respect VMs are different than real machines.
If you try to test your PE on how it boots on a physical machine with Windows 7 - testing in a VM only gives you useful results if you set the VM to guestOS windows8.
That behaviour is very different to real hardware.
I thought you had a problem booting PE 4 at all.
Just for fun I tried to boot the pe as guestOS "ms-dos" - on my host that also works - but it is significantly slower.
Here it only fails to boot when I use EFI firmware and dont have a harddisk in the VM.
Does it work for you when the VM use lsi-sas or lsi scsi-controller and fails for every other controller ?